Hercules by Bathmate isn't a penis pump like you know it. It uses hydraulic pressure to expand the blood vessels and tissue in the penis. Through daily use, the results will become permanent. Because water creates a far more powerful vacuum than air, which in turn leads to greater power to increase penis size, the Hercules is far superior to any air pump. Temporary gains in length, girth erectile strength and stamina will occur after your very first use. These results may range from .25" to 1.00" in girth. Length varies with participant, but all gains improve with time.